Energy vs. Power: What's the Difference?
Read the comparison below, or explore it visually. Create a visual lesson comparing energy and power using available credits or plan allowance.
Energy is the capacity to do work, while power is the rate at which energy is transferred or used. Energy is measured in joules and power in watts, where one watt is one joule per second; on an electricity bill, an appliance's power is rated in kilowatts (kW), and the energy it consumes over time is charged in kilowatt-hours (kWh).
At a glance
| Energy | Power | |
|---|---|---|
| Definition | Capacity to do work | Rate of doing work or using energy |
| SI unit | Joule (J) | Watt (W) = joule per second |
| Electricity-bill unit | Kilowatt-hour (kWh), the billing 'unit' | Kilowatt (kW), an appliance's rating |
| Formula | Energy = power × time | Power = energy ÷ time |
| Example | A 2 kW geyser run for 1 hour uses 2 kWh | That geyser draws 2 kW whenever it is on |
Which should you use?
Energy is the quantity to track for cost and fuel, such as the kWh units on a monthly electricity bill or the kilojoules of food energy printed on a biscuit packet.
Power is the quantity to check for capacity, such as whether a 5 kW household connection can run a 1.5 kW air conditioner and a 2 kW geyser at the same time.